1. Field of the Invention
The present invention relates in general to improved trucks for railway cars. More specifically, but without restriction to the particular use which is shown and described, this invention relates to underslung equalizer beams that are hot-box detector compatible and accomodate conventional brake beams.
2. Description of the Related Art
Equalizer beams are a device in the railroad industry whose purpose is to provide superior wheel load equalization. Wheel load equalization is a measure of the railway tuck's ability to safely traverse uneven railroad track where one wheel is raised or lowered relative to the other three wheels. With conventional trucks, primary spring suspensions are located on the vertical center line of the axles. In contrast, with an equalizer spring truck, the primary suspension (equalizer springs) is located atop the equalizer beam and inboard of the axle center lines. By locating the primary suspension longitudinally inboard of the axle center lines, springs of the same rate provide superior wheel load equalization compared to springs at the axles. The reason for the superior wheel load equalization with the primary suspension inboard of the axle center lines is based on the location of the primary springs. With springs at the axle centerline, when one wheel is raised, the primary spring at that journal must deflect an amount equal to the wheel rise. With an equalizer beam, when one wheel is raised, the primary spring (equalizer spring) only has to deflect a fraction of the wheel rise because of the location of the spring. Thus, for primary springs of equal rate, the equalizer beam truck provides dramatically better wheel load equalization compared to springs located at the axleboxes. Consequently, for high speed operation on rough track, the equalizer beam truck is superior in safety.
Conventional equalizer beams longitudinally span the spaced-apart axles of the truck wheels. The equalizer beams have a generally drop or "gooseneck" shape at each end so that the beam is supported atop the axleboxes. Near its center, the equalizer beam drops down to support the equalizer springs. Traditionally, there are two types of equalizer beams, the single equalizer and the dual equalizer. The single equalizer has only one beam on each side of the truck passing through the bottom wall of the truck frame on the journal centerline. The dual equalizer beam uses two beams on each side of the truck located equidistant transversely inboard and outboard of the truck frame. The dual equalizers are, of course, more costly than a single beam, but do not pass through the truck frame.
Conventionally, equalizer beams have been steel forgings. The dies and consequently the forged beams were and still are very expensive. In the recent past, safe equalizer beams have been manufactured from high-strength steel plates. However, steel plate is still expensive and because of the drop or "gooseneck" shape of the equalizer beams, cutting of the beams results in a significant amount of offal. Moreover, as will be more fully discussed below, conventional equalizer beams shield a significant portion of the axle bearings from view and thus prevent the detection of overheated axle bearings by wayside hot-box detectors.
One of the more serious problems with railway cars and more specifically with the axle bearings is that as the bearings wear out, the bearings will overheat and potentially cause serious railcar derailments. In the past, the detection of overheating axle bearings required the train crew in the caboose, while the train was in transit, to monitor the truck wheels for bearing smoke which indicated overheating. Today, the railroad industry uses what are termed hot-box detection scanners which are located along the side of the railroad track. These scanners, also known as hot-box detectors, monitor the temperature of the axle bearings by sensing the temperature of each bearing as the train travels by. As the train continues past the detector, the detector signals to the train engineer how many axle bearings it scanned, how many bearings were good and how many were bad, that is, too hot. The detector also signals where the hot bearings are located.
For the hot-box detectors to work effectively, the detectors must be able to sense the axle bearings and not be obstructed by truck component structure. To ensure the hot-box detectors have an unobstructed view of the axle bearings, the Association of American Railroads "AAR" sets forth criteria for limiting the location of component structure around the axle bearings, to permit unrestricted interchange of the car. This criteria prohibits obstruction of the axle bearings by surrounding component structure and thus allows temperature sensing by the hot-box detectors located along the side of the railroad track.
Thus, it is highly desirable to incorporate an equalizer beam with high-speed freight and passenger trucks that does not require the conventional drop shape and which is also hot-box detector compatible. However, challenges must be overcome. Cost and assembly and disassembly of parts is always a concern in the freight industry. In addition, since the wheelbase must be short in freight trucks, conventional single equalizer beams mounted atop the axlebox are impractical because the drop or vertical portion of the beam must be fitted between the inner pedestal jaw and the equalizer spring seat thereby necessitating an extended wheelbase. Conventional dual equalizer beams obstruct large portions of the journal bearing assemblies rendering the conventional dual equalizer beam unacceptable for unrestricted interchange service. Further, freight trucks require an unsprung location for mounting conventional brake beam guides. The only practical location to mount brake beam guides on an equalizer beam truck is off the equalizer beam.
Most passenger railcars use conventional equalizer beams, that is, beams that span the truck axles and set on top of the axleboxes. It is advantageous and highly desirable to use an equalizer beam that is hot-box detector compatible so as to not interfere with the axle bearing temperature detection scanners. Accordingly, an object of the present invention is to overcome the problems associated with conventional equalizer beams on freight and passenger vehicles and still provide an equalizer beam that does not interfere with the hot-box scanners. It is a further object of the present invention to provide an equalizer beam that utilizes conventional brake beam guides and reduces the maintenance costs associated with removal and replacement of the conventional brake beams. Still further, an object of the present invention is to minimize cost and weight of equalizer beams and to make assembly and disassembly of an equalizer beam more efficient. In addition, it is an object of the invention to minimize the truck wheelbase.